Retirement Plans and Other Benefits (Details) (USD $)	1 Months Ended	12 Months Ended
	Jul. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Retirement Plans and Other Benefits
Amount of pension and other postretirement benefit costs deferred			$ 14,000,000	$ 11,000,000
Regulatory asset amortization period	3 years
Amortization of regulatory assets		8,000,000	4,000,000
Amounts recognized on the Consolidated Balance Sheets
Noncurrent liability		(513,628,000)	(1,058,755,000)
Pension Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period		64,195,000	63,502,000	57,605,000
Interest cost on benefit obligation		112,392,000	119,586,000	124,727,000
Expected return on plan assets		(146,333,000)	(140,979,000)	(133,678,000)
Amortization of prior service cost (credit)		1,097,000	1,143,000	1,400,000
Amortization of net actuarial loss		39,852,000	44,250,000	25,956,000
Net periodic benefit cost		71,203,000	87,502,000	76,010,000
Portion of cost charged to expense		38,968,000	36,333,000	29,312,000
Change in Benefit Obligation
Benefit obligation at the beginning of the period		2,850,846,000	2,699,126,000
Service cost		64,195,000	63,502,000	57,605,000
Interest cost		112,392,000	119,586,000	124,727,000
Benefit payments		(125,269,000)	(113,632,000)
Actuarial (gain) loss		(255,634,000)	82,264,000
Benefit obligation at the end of the period		2,646,530,000	2,850,846,000	2,699,126,000
Change in Plan Assets
Balance at the beginning of the period		2,079,181,000	1,850,550,000
Actual return on plan assets		150,546,000	259,363,000
Employer contributions		140,500,000	65,000,000	0
Benefit payments		(106,106,000)	(95,732,000)
Balance at the end of the period		2,264,121,000	2,079,181,000	1,850,550,000
Funded Status at the end of the period		(382,409,000)	(771,665,000)
Projected benefit obligation and the accumulated benefit obligation for pension plans with an accumulated obligation in excess of plan assets
Projected benefit obligation		2,646,530,000	2,850,846,000
Accumulated benefit obligation		2,469,889,000	2,646,306,000
Fair value of plan assets		2,264,121,000	2,079,181,000
Amounts recognized on the Consolidated Balance Sheets
Current liability		(10,860,000)	(19,107,000)
Noncurrent liability		(371,549,000)	(752,558,000)
Net amount recognized		(382,409,000)	(771,665,000)
Other Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period		23,597,000	27,163,000	21,856,000
Interest cost on benefit obligation		41,536,000	46,467,000	46,807,000
Expected return on plan assets		(45,717,000)	(45,793,000)	(41,536,000)
Amortization of transition obligation			452,000	452,000
Amortization of prior service cost (credit)		(179,000)	(179,000)	(179,000)
Amortization of net actuarial loss		11,310,000	20,233,000	15,015,000
Net periodic benefit cost		30,547,000	48,343,000	42,415,000
Portion of cost charged to expense		18,469,000	19,321,000	15,208,000
Change in Benefit Obligation
Benefit obligation at the beginning of the period		990,418,000	1,047,094,000
Service cost		23,597,000	27,163,000	21,856,000
Interest cost		41,536,000	46,467,000	46,807,000
Benefit payments		(26,675,000)	(26,279,000)
Actuarial (gain) loss		(138,458,000)	(104,027,000)
Benefit obligation at the end of the period		890,418,000	990,418,000	1,047,094,000
Change in Plan Assets
Balance at the beginning of the period		684,221,000	608,663,000
Actual return on plan assets		76,995,000	83,567,000
Employer contributions		14,438,000	22,707,000	19,000,000
Benefit payments		(27,315,000)	(30,716,000)
Balance at the end of the period		748,339,000	684,221,000	608,663,000
Funded Status at the end of the period		(142,079,000)	(306,197,000)
Amounts recognized on the Consolidated Balance Sheets
Noncurrent liability		(142,079,000)	(306,197,000)
Net amount recognized		$ (142,079,000)	$ (306,197,000)